Thin film magnetic head

ABSTRACT

A thin film magnetic head includes an upper shield section, a lower shield section and a magnetoresistance device section between the upper shield section and the lower shield section. The magnetoresistance device section is connected to the upper shield section and the lower shield section through conductive layers. Current flows through the magnetoresistance device section via the upper shield and the lower shield.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a thin film magnetic heademploying a magnetoresistance effect device (hereinafter, referred to asan MR device). In particular, the present invention relates to a thinfilm magnetic head for significantly high density magnetic recordinghaving a remarkably narrow shield gap length.

[0003] 2. Description of the Related Art

[0004] A thin film magnetic head employing an MR device have long beenunder development. FIG. 6 shows a cross-sectional view of a thin filmmagnetic head having a conventional MR device.

[0005] The conventional thin film magnetic head 200 includes a recordinghead section 180 and a reproducing head section 190. The recording headsection 180 includes head cores 12 and 13 formed of magnetic substances,and a recording gap 14 formed of a non-magnetic insulating film. Inaddition, a winding conductor 11 is provided through the non-magneticinsulating film. In the recording head section 180, a magnetic fieldgenerated by current flowing through the winding conductor 11 isconverged to the head cores 12 and 13, and thus recording to a medium isperformed by the magnetic field leaked from the recording gap 14. Thistype of recording head section 180 is referred to as an inductive typerecording head.

[0006] On the other hand, the reproducing head section 190 includes anupper shield 13 (functioning as the recording head core 13) and a lowershield 16 formed of magnetic films, and an MR device section 15 in ashield gap 17 between the upper and lower shields 13 and 16. The MRdevice section 15 is insulated from the upper shield 13 and the lowershield 16 by insulating films 18. A lead section 19 is formed so as tosupply current in a direction of the plane of the thin film MR devicesection 15. Conventionally, as a material for the MR device section 15,a permalloy (e.g., Ni_(0.8)Fe_(0.2)) is used. The reproducing headsection 190, which is a magnetoresistance effect type head, detects achange in a signal magnetic field from a medium as a change in theelectric resistance of the MR device section 15, and this makes itpossible for the head section 190 to read out a signal recorded in themedium.

[0007] However, the following problems arise in achieving high densityrecording when the conventional technique described above is used. Sincea shield gap length (denoted by d_(sg) in FIG. 6) is required to beequal to or shorter than the shortest signal wavelength to bereproduced, it is necessary to further reduce the thicknesses of theinsulating films 18 and the MR device section 15 with furtherdevelopment of high density recording. In the future, the shield gaplength is expected to be about 100 nm or less, and there will be a needfor the thickness of the insulating film 18 to be about 50 nm or less.However, to the detriment of achieving high density recording, it istechnically difficult to form an insulating film having a thickness ofabout 50 nm or less and maintain good insulating properties.

SUMMARY OF THE INVENTION

[0008] A thin film magnetic head according to the present inventionincludes an upper shield section, a lower shield section and amagnetoresistance device section. The magnetoresistance device sectionis between the upper shield section and the lower shield section. Themagnetoresistance device section is connected to the upper shieldsection and the lower shield section through conductive layers. Currentflows through the magnetoresistance device section via the upper shieldand the lower shield.

[0009] In one embodiment of the invention, the magnetoresistance devicesection includes a multilayer structure exhibiting a giantmagnetoresistance effect.

[0010] In another embodiment of the invention, the current flows in adirection substantially perpendicular to a plane of the multilayerstructure.

[0011] In still another embodiment of the invention, the multilayerstructure includes a soft magnetic film. The magnetization easy axis ofthe soft magnetic film is substantially orthogonal to a direction of amagnetic field to be detected.

[0012] In yet another embodiment of the invention, the multilayerstructure includes a hard magnetic film, a soft magnetic film and anon-magnetic film formed between the hard magnetic film and the softmagnetic film. The magnetization easy axis of the hard magnetic filmsubstantially agrees with a direction of a magnetic field to bedetected.

[0013] In one embodiment of the invention, the thin film magnetic headfurther includes an interface magnetic film mainly composed of Co havinga thickness of about 0.1 to 1 nm at least one of interfaces between thenon-magnetic film and the hard magnetic film and between the nonmagneticfilm and the soft magnetic film.

[0014] In another embodiment of the invention, the magnetoresistancedevice section includes a plurality of multilayer structures.

[0015] In still another embodiment of the invention, themagnetoresistance device section includes a plurality of multilayerstructures.

[0016] In yet another embodiment of the invention, the magnetoresistancedevice section further includes a nonmagnetic film between the pluralityof multilayer structures.

[0017] In on e embodiment of the invention, the magnetoresistance devicesection further includes a nonmagnetic film between the plurality ofmultilayer structures.

[0018] In another embodiment of the invention, the multilayer structureincludes a metal anti-ferromagnetic film, a first magnetic filmmagnetically coupled to the metal anti-ferromagnetic film, a softmagnetic film and a non-magnetic film formed between the first magneticfilm and the soft magnetic film in this order. The magnetization easyaxis of the first magnetic film substantially agrees with a direction ofa magnetic field to be detected.

[0019] In still another embodiment of the invention, the multilayerstructure further includes an interface magnetic film mainly composed ofCo having a thickness of about 0.1 to 1 nm at least one of interfacesbetween the non-magnetic film and the first magnetic film and betweenthe non-magnetic film and the soft magnetic film.

[0020] In yet another embodiment of the invention, the magnetoresistancedevice section includes a plurality of multilayer structures.

[0021] In one embodiment of the invention, the magnetoresistance devicesection includes a plurality of multilayer structures.

[0022] In anther embodiment of the invention, the magnetoresistancedevice section further includes a nonmagnetic film between the pluralityof multilayer structures.

[0023] In still another embodiment of the invention, themagnetoresistance device section further includes a nonmagnetic filmbetween the plurality of multilayer structures.

[0024] In yet another embodiment of the invention, the non-magnetic filmincludes a first non-magnetic film, a second non-magnetic film and athird non-magnetic film interposed between the first non-magnetic filmand the second non-magnetic film. The second non-magnetic film has athickness of about 0.1 to 1 nm and is formed of a different materialfrom the first non-magnetic film and the second non-magnetic film.

[0025] In one embodiment of the invention, the nonmagnetic film includesa first non-magnetic film, a second non-magnetic film and a thirdnon-magnetic film interposed between the first non-magnetic film and thesecond non-magnetic film. The second non-magnetic film has a thicknessof about 0.1 to 1 nm and is formed of a different material from thefirst non-magnetic film and the second non-magnetic film.

[0026] In another embodiment of the invention, the soft magnetic film ismainly composed of Ni_(X)Co_(Y)Fe_(Z), where X is 0.6 to 0.9, Y is 0 to0.4 and Z is 0 to 0.3 in an atomic composition ratio.

[0027] In still another embodiment of the invention, the soft magneticfilm is mainly composed of Ni_(X′)Co_(Y′)Fe_(Z′), where X′ is 0 to 0.4,Y′ is 0.2 to 0.95 and Z′ is 0 to 0.5 in an atomic composition ratio.

[0028] In yet another embodiment of the invention, the soft magneticfilm is formed of an amorphous material.

[0029] In one embodiment of the invention, the nonmagnetic film isformed of any one of materials selected from Cu, Ag and Au.

[0030] In another embodiment of the invention, the non-magnetic film isformed of any one of materials selected from Cu, Ag and Au.

[0031] In still another embodiment of the invention, the first andsecond non-magnetic films are formed of Cu, and the third non-magneticfilm is formed of Ag.

[0032] In yet another embodiment of the invention, the first and secondnon-magnetic films are formed of Cu, and the third non-magnetic film isformed of Ag.

[0033] In one embodiment of the invention, the nonmagnetic film is anoxide thin film.

[0034] In another embodiment of the invention, the nonmagnetic film isan oxide thin film.

[0035] In still another embodiment of the invention, the oxide thin filmis formed of aluminum oxide.

[0036] In yet another embodiment of the invention, the oxide thin filmis formed of aluminum oxide.

[0037] In one embodiment of the invention, the hard magnetic film isformed of a material mainly composed of Co.

[0038] In another embodiment of the invention, a ratio of remnantmagnetization to a saturation magnetization of the hard magnetic film isabout 0.7 or more.

[0039] In still another embodiment of the invention, the metalanti-ferromagnetic film is formed of any one of materials selected fromNiMn, IrMn and PtMn.

[0040] In one embodiment of the invention, the multilayer structureincludes a pair of magnetic films and a non-magnetic film interposedbetween the pair of magnetic films. The pair of magnetic films are apair of soft magnetic films coupled in an anti-ferromagnetic exchangeinteraction.

[0041] In another embodiment of the invention, the magnetoresistancedevice section includes a plurality of multilayer structures.

[0042] In still another embodiment of the invention, the non-magneticfilm is formed of any one of materials selected from Cu, Ag and Au.

[0043] According to the thin film magnetic head of the presentinvention, since the MR device section and the upper shield and thelower shield are connected to each other by conductive layers, the uppershield and the lower shield function as the lead section as well. Theconductive layers can be easily made as thin as about 20 nm or less.Therefore, the thin film magnetic head of the present invention does notrequire very thin insulating films between the MR device section and theshields, thus eliminating the problems involved with minimizing gap inthe insulating film and making the thickness of the MR device sectionvery thin.

[0044] Furthermore, when the multilayer structure (artificialmultilayers) exhibiting a giant magnetoresistance effect (GMR) is usedin the MR device section, the multilayer structure exhibits a larger MRratio in the case where the direction of sense current is perpendicularto the film plane than in the case where it is parallel to the planedirection (see, for example, J. Appl. Phys., 75(10), May 15, 1994 pp.6709-6713). Therefore, a larger reproduction output can be obtained.

[0045] Thus, the invention described herein makes possible the advantageof providing a thin film magnetic head for very high density magneticrecording having a remarkably narrow shield gap length.

[0046] This and other advantages of the present invention will becomeapparent to those skilled in the art upon reading and understanding thefollowing detailed description with reference to the accompanyingfigures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0047]FIG. 1 is a cross-sectional view of a part of a thin film magnetichead according to the present invention;

[0048]FIG. 2A is a cross-sectional view of an MR device section having abasic structure used in the magnetic head according to the presentinvention;

[0049]FIG. 2B is a cross-sectional view of a stacked type MR devicesection having a plurality of the structure shown in FIG. 2A;

[0050]FIG. 3A is a cross-sectional view of another MR device sectionhaving a basic structure used in the magnetic head according to thepresent invention;

[0051]FIG. 3B is a cross-sectional view of a stacked type MR devicesection having a plurality of the structure shown in FIG. 3A;

[0052]FIG. 4A is a cross-sectional view of still another MR devicesection having a basic structure used in the magnetic head according tothe present invention;

[0053]FIG. 4B is a cross-sectional view of a stacked type MR devicesection having a plurality of the structure shown in FIG. 4A;

[0054]FIG. 5A is a cross-sectional view of still another MR devicesection having a basic structure used in the magnetic head according tothe present invention;

[0055]FIG. 5B is a cross-sectional view of a stacked type MR devicesection having a plurality of the structure shown in FIG. 5A; and

[0056]FIG. 6 is a cross-sectional view of a conventional thin filmmagnetic head.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0057]FIG. 1 shows a cross-sectional view of a thin film magnetic head100 according to the present invention. The thin film magnetic head 100includes a recording head section 20 and a reproducing head section 30.The recording head section 20 includes an upper head core 2 and a lowerhead core 3 formed of magnetic substances, and a recording gap 4 formedof a non-magnetic insulating film. In addition, a winding conductor 1 isprovided through the non-magnetic insulating film forming the recordinggap 4. In the recording head section 20, a magnetic field generated bycurrent flowing through the winding conductor 1 is converged to theupper head core 2 and the lower head core 3, and thus recording to amedium is performed by the magnetic field leaked from the recording gap4. This type of recording head is referred to as an inductive typerecording head. The general structure of the recording head section 20is the same as that of the conventional thin film magnetic head section200 shown in FIG. 6.

[0058] The reproducing head section 30 includes an upper shield 3(functioning as the lower head core 3 of the recording head section 20)and a lower shield 6 formed of magnetic films, and an MR device section5 disposed in a shield gap 7 between the upper and lower shields 3 and6. The structure of the reproducing head section 30 is different fromthat in the conventional thin film magnetic head.

[0059] The MR device section 5 in the shield gap 7 is interposed betweenthe upper shield 3 and the lower shield 6 via conductive layers 10 a and10 b. The upper shield 3 and the lower shield 6 function as a leadsection for supplying sense current to the MR device section 5 as well.The upper and lower shield 3 and 6 are made of a metal material (e.g.,Fe—Si—Al or the like) having an electric conductivity. An insulatingfilm 8 is formed in a portion where the MR device section 5 is notdisposed in the shield gap 7. In the thin film magnetic head 100according to the present invention, sense current flows in a directionperpendicular to the plane of the thin film MR device section 5.

[0060] In the conventional thin film magnetic head 200, the MR devicesection 15 is interposed between the upper shield 13 and the lowershield 16 via the insulating films 18. On the other hand, in the thinfilm magnetic head 100 of the present invention, the MR device section 5is interposed between the upper shield 3 and the lower shield 6 via theconductive layers 10 a and 10 b. Since it is possible to more easilymake the conductive layers very thin than the insulating films, theconductive layer 10 a and 10 b can be formed to a thickness of about 20nm or less. Therefore, according to the present invention, the problemsassociated with the above-mentioned conventional techniques with respectto minimizing the gap of the insulating film and making the thickness ofthe MR device section very thin are overcome.

[0061] Furthermore, a permalloy (single layer) used as the magneticmaterial in the conventional MR device section does not exhibit amagnetoresistance effect, even if sense current flows in a directionperpendicular to the magnetic layer (in a direction of the thickness ofthe layer). Therefore, even if the structure of the present invention isapplied to that case, the thin film magnetic head does not sufficientlyfunction as such. It is preferable to employ artificial multilayers(multilayer structure) which exhibit a giant magnetoresistance effect(GMR) as the MR device section 5 in the thin film magnetic head of thepresent invention. This is because the artificial multilayers having aGMR exhibit a larger ratio of change in magnetoresistance (hereinafter,referred to as an MR ratio) in the case where the sense current flows inthe direction perpendicular to the film plane than in the case where itflows in a direction parallel to the film plane. The MR ratio is definedby the following equation:

MR ratio (%)=(R(maximum)−R(minimum))/R(minimum)×100

[0062] Next, an example of the MR device section having a multilayerstructure suitably employed in the thin film magnetic head of thepresent invention will be described below.

[0063] An MR device section (multilayer structure) 50 shown in FIG. 2Aincludes a hard magnetic film 51, a soft magnetic film 53 and anon-magnetic film 52 interposed between the hard magnetic film 51 andthe soft magnetic film 53. The non-magnetic film 52 is formed in orderto weaken magnetic coupling between the hard magnetic film 51 and thesoft magnetic film 53. A material which has a good square feature ofmagnetization curve is preferable for the hard magnetic film 51, andpreferably, the hard magnetic film 51 is formed in such a manner thatthe direction of the magnetic field (a signal magnetic field of themedium or the like) to be detected is identical with the magnetizationeasy axis direction of the hard magnetic film 51. In the MR devicesection 50, only the magnetization direction of the soft magnetic film53 is rotated (inverted) by the signal magnetic field, and themagnetization direction of the hard magnetic film 51 is not rotated.Thus, the electric resistance varies depending on the angle formed bythe directions of the magnetization of the soft magnetic film 53 and themagnetization of the hard magnetic film 51. It is preferable that themagnetization easy axis of the soft magnetic film be substantiallyorthogonal to the direction of a magnetic field to be detected in orderto obtain an output which provides good linearity and reduced noise.

[0064] In this specification, a magnetic film having a coercive force of100 Oe or more is referred to as “a hard magnetic film”, and a magneticfilm having a coercive force of 20 Oe or less is referred to as “a softmagnetic film”.

[0065] The operation principle of the MR device section 50 will bedescribed below. In the case where the hard magnetic film 51 isunidirectionally magnetized by a ferromagnetic field, when a weak signalmagnetic field having a direction opposite to the direction in which thehard magnetic film 51 is magnetized is applied to the MR device section50, the magnetization of the hard magnetic film 51 is not rotated, butthe magnetization of the soft magnetic film 53 is rotated to thedirection of the signal magnetic field. As a result, the magnetizationdirection of the hard magnetic film 51 is anti-parallel to themagnetization direction of the soft magnetic film 53. When themagnetization direction of the hard magnetic film 51 is anti-parallel tothat of the soft magnetic film 53, the electrons in a current flowingthrough the MR device section 50 is subjected to magnetic scattering,mainly at interfaces between the hard magnetic film 51 and thenon-magnetic film 52, and between the non-magnetic film 52 and the softmagnetic film 53. As a result, the electric resistance of the MR devicesection 50 increases. On the other hand, when a weak signal magneticfield having the same direction as the direction in which the hardmagnetic film 51 is applied to the MR device section 50, themagnetization direction of the hard magnetic film 51 is parallel to thatof the soft magnetic film 53. As a result, the above-mentioned magneticscattering is reduced so that the electric resistance of the MR devicesection 50 is reduced. On the basis of the above-mentioned principle,the MR device section 50 varies its electric resistance depending on thechange in the signal magnetic field. As described above, the change inthe electric resistance is caused by magnetic scattering of electrons atthe interfaces of the multilayer structure. Therefore, the change in theelectric resistance becomes larger with respect to the current flowingin a direction perpendicular to the main plane of the MR device section50. The main plane of the MR device section 50 refers a plane parallelto the plane defined by each layer constituting the multilayer structureand perpendicular to the stacked direction of the multilayer structure.

[0066] If necessary, a conductor line for a bias magnetic field forapplying a bias magnetization to the above-mentioned MR device section50 having the multilayer structure can be provided in the vicinity ofthe MR device section 50. Alternatively, in order to make at least thesoft magnetic film 53 of the MR device section 50 into a single magneticdomain, an anti-ferromagnetic film or a hard magnetic film may befurther attached to the end of the MR device section 50. This is truefor the structures described later.

[0067]FIG. 2B shows another structure of an MR device section preferablyemployed in the present invention. An MR device section 50′ shown inFIG. 2B has a structure where a multilayer of [the hard magnetic film51/the non-magnetic film 52/the soft magnetic film 53] shown in FIG. 2Ais stacked a plurality of times via the nonmagnetic film 52. Such astacked structure is represented by [the hard magnetic film 51/thenon-magnetic film 52/the soft magnetic film 53/the non-magnetic film52]^(N) (N indicates the number of repetitions). By adopting such astacked structure, the magnetic scattering at the interfaces between therespective films increases. Therefore, in the case where there is roomin the shield gap length, by employing the above-mentioned multilayerstructure, an MR device having a larger MR ratio can be obtained.

[0068]FIG. 3A shows an MR device section 60 in which, in thesandwich-type MR device section 50 shown in FIG. 2A, a magnetic film 53′(hereinafter, referred to as an interface magnetic film) is inserted atthe interface between the hard magnetic film 51 and the nonmagnetic film52. However, it should be appreciated that the interface magnetic film53′ may be formed between the non-magnetic film 52 and the soft magneticfilm 53. It is sufficient that the magnetic characteristics of theinterface magnetic film 53′ do not impair the magnetic characteristicsof the magnetic film in contact with the interface magnetic film 53′.More specifically, in the case where the interface magnetic film 53′ isinserted between the hard magnetic film 51 and the non-magnetic film 52,it is sufficient that the combination of the interface magnetic film 53′and the hard magnetic film 51 functions as a hard magnetic film. In thecase where the interface magnetic film 53′ is inserted between the softmagnetic film 53 and the non-magnetic film 52, it is sufficient that thecombination of the interface magnetic film 53′ and the soft magneticfilm 53 functions as a soft magnetic film.

[0069]FIG. 3B shows an MR device section 60′ in which, in thestacked-type MR device section 50′ shown in FIG. 2B, an interfacemagnetic film 53′ is inserted between the hard magnetic film 51 and thenon-magnetic film 52. In FIG. 3B, the interface magnetic film 53′ isprovided on both faces of the hard magnetic film 51, but it is alsoappreciated that the interface magnetic film 53′ may be provided on onlyone face of the hard magnetic film 51. The MR device section 60′ shownin FIG. 3B shows a larger MR ratio, as compared with the MR devicesection 60 shown in FIG. 3A.

[0070] In the case where the stacked-type MR device section shown inFIGS. 2B and 3B is used, it is preferable that the respectivethicknesses of the hard magnetic film 51, the non-magnetic film 52, thesoft magnetic film 53 and the interface magnetic film 53′ are not verylarge in view of the mean free path of electrons. More specifically, itis preferable that the respective thicknesses are about 6 nm or less.Furthermore, although the MR ratio increases with increasing the numberof stacks of components, the effect is remarkably observed when thecomponents are stacked three times or more. The effect is substantiallysaturated when the components are stacked ten times or more.

[0071]FIGS. 4A and 4B show other examples of a multilayer structureusing an anti-ferromagnetic film in another structure of the MR devicesection according to the present invention.

[0072] An MR device section(multilayer structure) 70 shown in FIG. 4Ahas a structure where a metal anti-ferromagnetic film 54, a magneticfilm 51′, a non-magnetic film 52, an interface magnetic film 53′ and asoft magnetic film 53 are stacked in this order. The magnetic film 51′and the metal anti-ferromagnetic film 54 stacked thereon function in thesame manner as the hard magnetic film 51 of the MR device section shownin FIGS. 2A and 3A. Alternatively, the interface magnetic film 53′ canbe omitted. The non-magnetic film 52 interposed between the magneticfilm 51′ and the soft magnetic film 53 is formed in order to weakenmagnetic coupling between the magnetic film 51′ and the soft magneticfilm 53. Furthermore, the interface magnetic film 53′ improves magneticscattering of electron spin at the interface, thus advantageouslyraising the MR ratio. The interface magnetic film 53′ may be formedbetween the non-magnetic film 52 and the magnetic film 51′, or may beformed on both faces of the non-magnetic film 52. A thickness of theinterface magnetic film 53′ is preferably about 0.1 to about 2 nm, andmore preferably in the range of about 0.5 to about 1.5 nm, and theinterface magnetic film 53′ is preferably formed of a material mainlycomposed of Co (over 50 atomic % in the case of a binary system, andover 33.3 atomic % in the case of a ternary system).

[0073] In the MR device section 70, only the magnetization of the softmagnetic film 53 is rotated by the signal magnetic field, and themagnetization of the magnetic film 51′ is not rotated. The electricresistance varies depending on the angle formed by the directions of themagnetization of the soft magnetic film 53 and the magnetization of themagnetic film 51′. The MR device section 70 is preferably formed in sucha manner that the magnetization easy axis direction of the magnetic film51′ is identical with the direction of the signal magnetic field.

[0074] Furthermore, in the case where there is room in the shield gaplength, as shown in FIG. 4B, when the structural unit shown in FIG. 4Ais stacked a plurality of times to form the MR device section 70′, afurther larger MR ratio can be obtained.

[0075] In the above-mentioned MR device section, especially, whenanother non-magnetic film of 0.1 to 1 nm having an effect of weakeningmagnetic coupling between the magnetic films is further provided in thenon-magnetic film, the magnetization of the soft magnetic film sectionis rotated more smoothly, resulting in an improvement of the magneticfield sensitivity of the MR device section. In this case, when Cu isused as a material for the non-magnetic film, and Ag as a material forthe non-magnetic film, more significant effect can be obtained.

[0076] Furthermore, when the soft magnetic film is mainly composed ofNi_(X)Co_(Y)Fe_(Z) (where X is 0.6 to 0.9, Y is 0 to 0.4 and Z is 0 to0.3 in an atomic composition ratio), a MR device section having goodsensitivity can be obtained. When the soft magnetic film is mainlycomposed of Ni_(X′)Co_(Y′)Fe_(Z′) (where X′ is 0 to 0.4, Y′ is 0.2 to0.95 and Z′ is 0 to 0.5 in an atomic composition ratio), an MR devicesection which shows a relatively large MR ratio can be obtained. When anamorphous magnetic film such as Co—Mn—B, Co—Fe—B or the like is used asa material for the soft magnetic film, The obtained MR device sectionexhibits soft magnetism even if it has thin thickness, and exhibits theGMR characteristics.

[0077] It is preferable to use a metal material as a material for thenon-magnetic film, and it is especially preferable to use any one of Cu,Ag and Au, because the obtained MR device section exhibits good GMRcharacteristics. The non-magnetic film may be formed of a tunnel GMRfilm made of a thin oxide thin film. In this case, since the electricresistance of the MR device section can be sufficiently enlarged withrespect to the lead section, the MR device section can be madesignificantly thin. Thus, a thin film magnetic head having a very narrowshield gap can be easily formed. An oxide of Al (Al₂O₃) is desirable asa material for the oxide thin film. Furthermore, the non-magnetic filmmay be a film formed of a mixture of an oxide and a metal (e.g., a filmwhere a column-like conductor exists as a conducting channel in theoxide).

[0078] When the hard magnetic film is mainly composed of Co (over 50atomic % in the case of a binary system, and over 33.3 atomic % in thecase of a ternary system), a large MR ratio can be obtained. It ispreferable that the magnetization curve of the hard magnetic filmpreferably used in the present invention has a good square feature. Inthis specification, a “good square feature” is defined so that thesquare ratio S (=remnant magnetization/saturation magnetization) is 0.7or more. When the square ratio S is smaller than 0.7, the MR curve inthe vicinity of the zero magnetic field deteriorates. The deteriorationof the MR curve in the vicinity of the zero magnetic field causes thereproduction sensitivity and the linearity of the magnetoresistive typehead. It is desirable that the square ratio of the hard magnetic film be0.7 or more in order to obtain a MR device section having good linearityand a large MR ratio.

[0079] A metal material having conductivity is preferable as a materialfor the anti-ferromagnetic film. More specifically, NiMn, IrMn and PtMncan preferably be used. An oxide anti-ferromagnetic substance is notpreferable, because it usually exhibits anti-ferromagnetism only whenits thickness is 10 to 50 nm or more, and the electric resistance ishigh.

[0080] As the structure of the MR device section, structures other thanthe above-mentioned structure can be used, such as MR device sections 80and 80′ shown in FIGS. 5A and 5B. The MR device section 80 includes twomagnetic films 81 and 81′ of the same type (i.e., two soft magneticfilms or two hard magnetic films), which are coupled in ananti-ferromagnetic exchange interaction via a non-magnetic film 82 suchas Cu, Ag, Au or the like. Alternatively, the MR device section 80′having a structure where the above-mentioned structure is stacked aplurality of times may be used. A large MR ratio can be obtained withthis structure. However, the sensitivity is deteriorated to some extentwith this structure. It is preferable that the two magnetic films 81 and81′ be soft magnetic films to reduce the degradation of the sensitivity.

[0081] The hard magnetic film and the soft magnetic film can be formedof the above-mentioned materials. In the case where the thickness of thenon-magnetic film 82 is in the vicinity of 2 nm, the two magnetic films81 and 81′ are coupled in an anti-ferromagnetic exchange interaction. Insuch MR device sections 80 and 80′, a large MR ratio can be obtained,but the sensitivity is less satisfactory than that of the MR devicesection described earlier. However, they can be applied to some uses.

EXAMPLES

[0082] Hereinafter, the present invention will be described by way ofexamples.

Example 1

[0083] In Example 1, a thin film magnetic head 100 (FIG. 1) having an MRdevice section 501 shown in FIG. 2B is fabricated as follows. First, aFe—Si—Al film (having a thickness of about 2 μm) is formed on asubstrate (e.g., a glass substrate) by sputtering to form a lower shield6. A Cu film having a thickness of about 20 nm is formed thereon bypatterning to form a conductive layer 10 a. The MR device section 50′(having a thickness of about 60 nm) made of [Co_(0.50)Fe_(0.50) (3nm)/Cu(2 nm)/Ni_(0.68)Fe_(0.20)Co_(0.12)(13 nm)/Cu(2 nm)]³ is formed onthe conductive layer 10 a by sputtering. A Cu film having a thickness ofabout 20 nm is formed on the MR device section 50′ by sputtering andpatterned to form a conductive layer 10 b. Thereafter, an Si₃N₄ filmhaving a thickness of about 100 nm is formed as an insulating film by areactive sputtering method. After throughholes are opened in the MRdevice section 50′, a Fe—Si—Al (having a thickness of about 2 μm) isformed by sputtering to form an upper shield 3.

[0084] Thereafter, a non-magnetic insulating film 4 having a windingconductor 1 and a head core 2 are formed to complete the thin filmmagnetic head 100. The nonmagnetic insulating film 4 and the head core 2can be formed by a known material and a known production method. Theobtained thin film magnetic head 100 having a narrow shield gap length(about 100 nm) provides a sufficient reproduction output.

Example 2

[0085] A thin film magnetic head of Example 2 is fabricated in the samemanner as Example 1, except that the MR device section 50′ is replacedby the MR device section 70 shown in FIG. 4A.

[0086] The MR device section 70 in Example 2 has a multilayer structureof [Ir_(0.20)Mn_(0.80)(10 nm)/Co_(0.50)Fe_(0.50) (4 nm)/Al₂O₃(5nm)/Co(0.8 nm)/Ni_(0.68)Fe_(0.20)CO_(0.12)(10.2 nm)] (a thickness ofabout 70 nm). As conductive layers 10 a and 10 b, Cu films having athickness of about 15 nm are formed. The thin film magnetic head ofExample 2 also provides sufficient reproduction output as in Example 1.

Example 3

[0087] A thin film magnetic head of Example 3 is fabricated in the samemanner as Example 2, except that Ni—Fe—Co is used as the material forthe lower shield 6, and the MR device section 70 is replaced by the MRdevice section 70 described below.

[0088] The MR device section 70 in Example 3 has a multilayer structureof [Ir_(0.20)Mn_(0.80)(8 nm)/Co(3 nm)/Al₂O₃ (5 nm)/Co_(0.90)Fe_(0.10)(1nm)/CoMnB(2 nm)] (a thickness of about 19 nm). As conductive layers 10 aand 10 b, Cu films having a thickness of about 20 nm are formed. As aninsulating film, an Si₃N₄ film having a thickness of about 60 nm isformed. The feature of this multilayer structure lies in that CoMnBwhich is amorphous is used as the material for the soft magnetic film.Although the thin film magnetic head of Example 3 has a narrow shieldgap length of about 60 nm, it also provides a sufficient reproductionoutput as in Example 1.

Example 4

[0089] A thin film magnetic head of Example 4 is fabricated in the samemanner as Example 1, except that the MR device section 50′ in Example 1is replaced by the MR device section 80′ shown in FIG. 5B.

[0090] The MR device section 80′ in Example 4 has a multilayer structureof [Ni_(0.68)Co_(0.20)Fe_(0.12)(3 nm)/Cu(2nm)/CO_(0.7)Fe_(0.20)Ni_(0.10)(3 nm)/Cu(2 nm)]6 (having a thickness ofabout 60 nm). Although the thin film magnetic head of Example 4 hasslightly lower sensitivity, it also provides a sufficient reproductionoutput as in Example 1.

Comparative Example 1

[0091] In Comparative Example 1, a conventional thin film magnetic head200 shown in FIG. 6 is fabricated as follows. First, a Fe—Si—Al film(having a thickness of about 2 μm) is formed on a glass substrate bysputtering to form a lower shield 16. Next, an Si₃N₄ film having athickness of about 40 nm is formed by a reactive sputtering method toform an insulating film 18 (in the lower portion). The MR device section15 made of [Co_(0.50)Fe_(0.50) (3 nm)/Cu(2nm)/Ni_(0.68)Fe_(0.20)Co_(0.12)(13 nm)/Cu(2 nm)] is formed on theinsulating film 18 (in the lower portion) by sputtering. An Si₃N₄ filmhaving a thickness of about 40 nm is further formed thereon bysputtering to form an insulating film 18 (in the upper portion). AFe—Si—Al (having a thickness of about 2 μm) is formed on the insulatingfilm 18 by sputtering to form an upper shield 13.

[0092] Thereafter, the thin film magnetic head 200 is fabricated in thesame manner as Example 1. Insulation is insufficient with the Si₃N₄ filmhaving a thickness of about 40 nm. Moreover, in the thin film magnetichead 200 of Comparative Example 1, leakage occurs between the MR devicesection 15 and the shield section 13 and/or 16, thus resulting in anunstable operation.

[0093] As described above, since the thin film magnetic head of thepresent invention does not require a very thin insulating film betweenthe shield section and the MR device section, the problem of minimizingthe gap of the insulating film in the conventional thin film magnetichead is eliminated, and a thin film magnetic head for very high densitymagnetic recording having a remarkable narrow shield gap length can beprovided. Moreover, when a multilayer structure exhibiting GMR is usedfor the MR device section, current flows in a direction perpendicular tothe film plane in the MR device section, thus obtaining a large magneticresistance effect.

[0094] Various other modifications will be apparent to and can bereadily made by those skilled in the art without departing from thescope and spirit of this invention. Accordingly, it is not intended thatthe scope of the claims appended hereto be limited to the description asset forth herein, but rather that the claims be broadly construed.

What is claimed is:
 1. A thin film magnetic head comprising an uppershield section, a lower shield section and a magnetoresistance devicesection, the magnetoresistance device section being between the uppershield section and the lower shield section, wherein themagnetoresistance device section is connected to the upper shieldsection and the lower shield section through conductive layers, andcurrent flows through the magnetoresistance device section via the uppershield and the lower shield.
 2. A thin film magnetic head according toclaim 1 , wherein the magnetoresistance device section comprises amultilayer structure exhibiting a giant magnetoresistance effect.
 3. Athin film magnetic head according to claim 2 , wherein the current flowsin a direction substantially perpendicular to a plane of the multilayerstructure.
 4. A thin film magnetic head according to claim 2 , whereinthe multilayer structure comprises a soft magnetic film, and themagnetization easy axis of the soft magnetic film is substantiallyorthogonal to a direction of a magnetic field to be detected.
 5. A thinfilm magnetic head according to claim 4 , wherein the multilayerstructure comprises a hard magnetic film, a soft magnetic film and anon-magnetic film formed between the hard magnetic film and the softmagnetic film, and the magnetization easy axis of the hard magnetic filmsubstantially agrees with a direction of a magnetic field to bedetected.
 6. A thin film magnetic head according to claim 5 , furthercomprising an interface magnetic film mainly composed of Co having athickness of about 0.1 to 1 nm at least one of interfaces between thenon-magnetic film and the hard magnetic film and between thenon-magnetic film and the soft magnetic film.
 7. A thin film magnetichead according to claim 5 , wherein the magnetoresistance device sectioncomprises a plurality of multilayer structures.
 8. A thin film magnetichead according to claim 6 , wherein the magnetoresistance device sectioncomprises a plurality of multilayer structures.
 9. A thin film magnetichead according to claim 7 , wherein the magnetoresistance device sectionfurther comprises a non-magnetic film between the plurality ofmultilayer structures.
 10. A thin film magnetic head according to claim8 , wherein the magnetoresistance device section further comprises anon-magnetic film between the plurality of multilayer structures.
 11. Athin film magnetic head according to claim 4 , wherein the multilayerstructure comprises a metal anti-ferromagnetic film, a first magneticfilm magnetically coupled to the metal anti-ferromagnetic film, a softmagnetic film and a non-magnetic film formed between the first magneticfilm and the soft magnetic film in this order, and the magnetizationeasy axis of the first magnetic film substantially agrees with adirection of a magnetic field to be detected.
 12. A thin film magnetichead according to claim 11 , wherein the multilayer structure furthercomprises an interface magnetic film mainly composed of Co having athickness of about 0.1 to 1 nm at least one of interfaces between thenon-magnetic film and the first magnetic film and between thenon-magnetic film and the soft magnetic film.
 13. A thin film magnetichead according to claim 11 , wherein the magnetoresistance devicesection comprises a plurality of multilayer structures.
 14. A thin filmmagnetic head according to claim 12 , wherein the magnetoresistancedevice section comprises a plurality of multilayer structures.
 15. Athin film magnetic head according to claim 13 , wherein themagnetoresistance device section further comprises a non-magnetic filmbetween the plurality of multilayer structures.
 16. A thin film magnetichead according to claim 14 , wherein the magnetoresistance devicesection further comprises a non-magnetic film between the plurality ofmultilayer structures.
 17. A thin film magnetic head according to claim5 , wherein the non-magnetic film comprises a first non-magnetic film, asecond non-magnetic film and a third non-magnetic film interposedbetween the first nonmagnetic film and the second non-magnetic film, andthe second non-magnetic film has a thickness of about 0.1 to 1 nm and isformed of a different material from the first non-magnetic film and thesecond nonmagnetic film.
 18. A thin film magnetic head according toclaim 11 , wherein the non-magnetic film/comprises a first nonmagneticfilm, a second non-magnetic film and a third non-magnetic filminterposed between the first nonmagnetic film and the secondnon-magnetic film, and the second non-magnetic film has a thickness ofabout 0.1 to 1 nm and is formed of a different material from the firstnon-magnetic film and the second nonmagnetic film.
 19. A thin filmmagnetic head according to claim 4 , wherein the soft magnetic film ismainly composed of Ni_(X)Co_(Y)Fe_(Z), where X is 0.6 to 0.9, Y is 0 to0.4 and Z is 0 to 0.3 in an atomic composition ratio.
 20. A thin filmmagnetic head according to claim 4 , wherein the soft magnetic film ismainly composed of Ni_(X′)Co_(Y′)Fe_(Z′), where X′ is 0 to 0.4, Y′ is0.2 to 0.95 and Z′ is 0 to 0.5 in an atomic composition ratio.
 21. Athin film magnetic head according to claim 4 , wherein the soft magneticfilm is formed of an amorphous material.
 22. A thin film magnetic headaccording to claim 5 , wherein the non-magnetic film is formed of anyone of materials selected from Cu, Ag and Au.
 23. A thin film magnetichead according to claim 11 , wherein the non-magnetic film is formed ofany one of materials selected from Cu, Ag and Au.
 24. A thin filmmagnetic head according to claim 17 , wherein the first and secondnon-magnetic films are formed of Cu, and the third/non-magnetic film isformed of Ag.
 25. A thin film magnetic head according to claim 18 ,wherein the first and second non-magnetic films are formed of Cu, andthe third non-magnetic film is formed of Ag.
 26. A thin film magnetichead according to claim 5 , wherein the non-magnetic film is an oxidethin film.
 27. A thin film magnetic head according to claim 11 , whereinthe non-magnetic film is an oxide thin film.
 28. A thin film magnetichead according to claim 26 , wherein the oxide thin film is formed ofaluminum oxide.
 29. A thin film magnetic head according to claim 27 ,wherein the oxide thin film is formed of aluminum oxide.
 30. A thin filmmagnetic head according to claim 5 , wherein the hard magnetic film isformed of a material mainly composed of Co.
 31. A thin film magnetichead according to claim 5 , wherein a ratio of remnant magnetization toa saturation magnetization of the hard magnetic film is about 0.7 ormore.
 32. A thin film magnetic head according to claim 11 , wherein themetal anti-ferromagnetic film is formed of any one of materials selectedfrom NiMn, IrMn and PtMn.
 33. A thin film magnetic head according toclaim 2 , wherein the multilayer structure comprises a pair of magneticfilms and a non-magnetic film interposed between the pair of magneticfilms, and the pair of magnetic films are a pair of soft magnetic filmscoupled in an anti-ferromagnetic exchange interaction.
 34. A thin filmmagnetic head according to claim 33 , wherein the magnetoresistancedevice section comprises a plurality of multilayer structures.
 35. Athin film magnetic head according to claim 33 , wherein the non-magneticfilm is formed of any one of materials selected from Cu, Ag and Au.